Porcelain composition

ABSTRACT

A ceramic composition includes a glass composition and a filler including at least one of Al 2 O 3  and TiO 2 , wherein the composition of the ceramic composition includes 0.15 to 0.55 mol of a, 0.45 to 0.85 mol of b, 0.01 to 0.2 mol of an oxide RO of an alkaline earth metal element R, and 0.1 to 0.4 mol of the filler, wherein a represents a molar quantity of an oxide Ln 2 O 3  of a rare earth element Ln, b represents a molar quantity of boron oxide B 2 O 3 , and a+b=1 mol.

TECHNICAL FIELD

The present invention relates to ceramic compositions. In particular, itrelates to a ceramic composition usable as, for example, a material fora multilayer substrate used for propagation of signals in ahigh-frequency band.

BACKGROUND ART

Recent years saw development in high-speed, large-capacity datacommunications and cellular communications. With respect to multilayersubstrates having integrated circuits, this development led to not onlysize-reduction and increased density but also investigations as to useof signals having frequencies in a high-frequency band ranging from, forexample, several ten megahertz to several hundred gigahertz. Whileceramic compositions are used in these multilayer substrates, it isdesirable that the ceramic compositions be made of a material(high-frequency band material) compatible with signals in thehigh-frequency band.

Typically, alumina (Al₂O₃) has been primarily used as the ceramiccomposition for the high-frequency band. As the density of theintegrated circuits increases, there has been developed a process ofmaking a multilayer substrate including an integrated circuit, theprocess including stacking a plurality of green sheets composed ofunsintered Al₂O₃, each green sheet having a conductor paste thatcontains a material for metal wiring applied by printing, and thensimultaneously baking the green sheets and the conductor paste. SinceAl₂O₃ sinters at a temperature as high as 1,500° C. to 1,600° C., a highmelting point-metal, such as tungsten or molybdenum, which can withstandsuch a high temperature, has been required as the material for the metalwiring of the integrated circuit.

The multilayer substrate has a problem in that it requires a largeamount of energy since the sintering temperature is high, therebyincreasing the manufacturing cost. Since the thermal expansioncoefficient of Al₂O₃ is larger than that of the IC chip, such as asilicon chip, in the integrated circuit, the multilayer substrate maysuffer from cracks depending on the operating temperature of themultilayer substrate. Furthermore, since the relative dielectricconstant of Al₂O₃ is large, the rate of signal propagation in theintegrated circuit has been low. Since the specific resistance of a highmelting point-metal, such as tungsten or molybdenum, is large comparedto that of Cu or Ag, which is suitable as a material for the metalwiring, the conductor loss due to the resistance of the metal wiringitself has also been large.

In view of the above, various ceramic compositions each in which afiller is incorporated in a glass composition have been developed as thematerial for multilayer substrates. Multilayer substrates using suchceramic compositions can be sintered at a temperature lower than thatwhen Al₂O₃ is used. Thus, it becomes possible to simultaneously sinterthe ceramic compositions and the material for metal wiring, such as Cuor Ag, having a smaller specific resistance. Furthermore, since thefiller is contained in the glass composition, the change in shape of theceramic composition can be reduced, and the strength of the ceramiccomposition can be increased.

For example, Japanese Examined Patent Application Publication No.3-53269 described an example of such a ceramic composition, prepared bysintering a mixture of a CaO—SiO₂—Al₂O₃—B₂O₃ glass composition and 50 to35 mass % of Al₂O₃ as a filler at 800° C. to 1,000° C. Japanese PatentNo. 3277169 discloses a ceramic composition containing 0 to 10 mol % ofAl₂O₃ as a filler and a glass composition including 50 to 67 mol % ofB₂O₃, 2 to 3 mol % of an oxide of an alkali metal element, 20 to 50 mol% of an oxide of an alkaline earth metal element, and 2 to 15 mol % ofan oxide of a rare earth element. Japanese Unexamined Patent ApplicationPublication No. 9-315855 discloses a ceramic composition containing anoxide of a rare earth element, Al₂O₃, CaO, and TiO₂, and in which thecompounding ratio of these components is limited within a particularrange.

The performances required for the ceramic composition for thehigh-frequency band include a low dielectric loss tanδ in thehigh-frequency band and a small absolute value of the temperaturecoefficient τ_(f) of the resonant frequency.

In other words, the loss in the course of signal propagation in thehigh-frequency band is preferably as small as possible. Thus, it isdesirable that the dielectric loss tanδ of the ceramic composition inthe high-frequency band be small, i.e., that the Q value (1/tan δ) belarge. Moreover, in order to yield stable performance from the ceramiccomposition serving as a dielectric member despite a temperature change,it is desirable that the absolute value of the temperature coefficientτ_(f) of the resonant frequency be small, i.e., that the temperaturedependence of the resonant frequency be low.

DISCLOSURE OF INVENTION

Under the above-described circumstances, an object of the presentinvention is to provide a ceramic composition that can be sintered at alow temperature and has a small dielectric loss in the high-frequencyband and a low temperature dependence of the resonant frequency.

An aspect of the present invention provides a ceramic compositionincluding a glass composition and a filler incorporated in the glasscomposition, the filler including at least one of Al₂O₃ and TiO₂,wherein the composition of the ceramic composition includes 0.15 to 0.55mol of a, 0.45 to 0.85 mol of b, 0.01 to 0.2 mol of an oxide RO of analkaline earth metal element R, and 0.1 to 0.4 mol of the filler,wherein a represents a molar quantity of an oxide Ln₂O₃ of a rare earthelement Ln, b represents a molar quantity of boron oxide B₂O₃, and a+b=1mol.

Preferably, the ceramic composition includes 0.05 mol or less oftungsten oxide WO₃, wherein a represents a molar quantity of an oxideLn₂O₃ of a rare earth element Ln, b represents a molar quantity of boronoxide B₂O₃, and a+b=1 mol.

Preferably, the ceramic composition includes 0.0005 to 0.002 mol of anoxide M₂O of an alkali metal element M, wherein a represents a molarquantity of an oxide Ln₂O₃ of a rare earth element Ln, b represents amolar quantity of boron oxide B₂O₃, and a+b=1 mol.

BEST MODE FOR CARRYING OUT THE INVENTION

The present inventor has conducted various studies on the composition inorder to obtain a ceramic composition that can be sintered at a lowtemperature and has a small dielectric loss in the high-frequency bandand a low temperature dependence of the resonant frequency.

It has been found that a ceramic composition in which a filler composedof an inorganic oxide is incorporated in a glass composition is mostsuitable as such a ceramic composition. The internal structure of theceramic composition is a network structure composed of a glasscomposition filling the gaps between the respective particles of thefiller. Since the material usable as the filler is limited within acertain range, the characteristics of the glass composition must beimproved to further improve the performance.

Thus, the material for the glass composition was studied first. Inparticular, the sintering temperature of the glass composition, thecompatibility with the filler, the relative dielectric constant, thedielectric loss in the high-frequency band, and the temperaturedependence of the resonant frequency were investigated. Of these items,the dielectric characteristic was measured by a dielectric resonatormethod (short-circuited at both ends of a dielectric resonator), i.e.,Hakki & Coleman method, using a cylindrical test sample after sintering.

In general, the dielectric loss is evaluated in terms of Q value, whichis obtained by the sharpness of the resonance. The Q value isfrequency-dependent and decreases in proportion to the frequency. Incontrast, the resonant frequency changes with the shape and thedielectric constant of the test sample. Thus, the dielectric loss of theceramic composition is evaluated by comparative assessment in terms ofthe product fQ of the resonant frequency fo and Q.

As a result of the studies on various glass compositions, it has beenfound that a glass composition containing a large amount of crystalsobtained by mixing an oxide Ln₂O₃ of a rare earth element (also referredto as “Ln”) and boron oxide B₂O₃ exhibits a particularly low dielectricloss. In this glass composition, crystals of LnBO₃, LnB₃O₆, Ln₃BO₃, orLn₄B₂O₉ appear depending on the compounding ratio, and the phase ofthese crystals presumably decreases the dielectric loss.

However, in order to adjust the composition of the glass compositioncomposed of only two components, i.e., Ln₂O₃ and B₂O₃, to yield a lowdielectric loss, the melting temperature must be increased, and thus,the sintering temperature required for obtaining a dense sinter becomeshigh. It was found that by adding an adequate amount of an oxide RO ofan alkaline earth metal element R (wherein R represents at least one ofMg, Ca, Sr and Ba) to the composition composed of Ln₂O₃ and B₂O₃, thesintering temperature can be decreased without significantly affectingthe dielectric loss.

Here, the target performance of the ceramic composition is set asfollows: that the value fQ (fo [GHz]×Q) at around 10 GHz is 15,000 orhigher; that the change in resonant frequency with temperature is small;and that the composition can be sintered at a temperature as low as1,000° C. or less, which is the temperature at which metal wiringcomposed of a highly conductive material, Ag or Cu, can besimultaneously formed to produce a multilayer substrate. Theinvestigations on the composition of the ceramic composition werecarried out based these. That the change in resonant frequency withtemperature be small is important for the stable operation of theintegrated circuit. The resonant frequency was measured while varyingthe temperature, and the rate of change in resonant frequency(temperature characteristic τ_(f)) with the varying temperature wasevaluated. The target range of the temperature characteristic τ_(f) ofthe resonant frequency was set to within ±50 ppm/° C. (−50 ppm/°C.≦τ_(f)≦+50 ppm/° C.).

It was also found that incorporation of tungsten oxide, WO₃, waseffective for decreasing the sintering temperature. It was found thatwhen an excessively large amount of WO₃ was incorporated, the change inresonant frequency with temperature tended to shift toward the negativeside.

It was found that incorporation of a small amount of an oxide M₂O of analkali metal element M (wherein M represents at least one selected fromLi, Na, and K) can further decrease the sintering temperature. Inparticular, incorporation of M₂O can effectively decrease the sinteringtemperature when a process of mixing all the starting materials and thensintering the resulting mixture in one step to obtain a ceramiccomposition is employed.

The filler is important for maintaining the strength of the ceramiccomposition and the shape during the sintering. Here, one or both ofAl₂O₃ and TiO₂ are used as the filler. When the strength is desired,Al₂O₃ is primarily used whereas TiO₂ is primarily used when a largedielectric constant is desired. However, when the amount of filler isexcessively large, the sintering temperature must be increased. When theamount of the filler is excessively small, the strength and the shapecan no longer be maintained. Thus, the amount of the filler is limitedby these factors.

The present invention has been made based on these results of studies byspecifically setting the limit of the composition range of the ceramiccomposition. The ceramic composition of the present invention includes aglass composition and a filler contained in the glass composition and issintered at a low temperature. The reasons for limiting the amount ofeach component of the composition are as follows.

Where the content of the oxide Ln₂O₃ of the rare earth element Ln in theceramic composition of the present invention is represented by a, thecontent of the boron oxide B₂O₃ in the ceramic composition of thepresent invention is represented by b, and a+b=1 mol, a is 0.15 to 0.55mol and b is 0.45 to 0.85 mol.

These content ranges are necessary for decreasing the dielectric loss inthe high-frequency band and for performing low-temperature sintering.When the contents of Ln₂O₃ and B₂O₃ are set as above, excellentdielectric characteristic, i.e., a high fQ value, can be yielded by thegeneration of crystals represented by Ln_(x)B_(y)O_(z) (wherein x, y,and z each represent an integer). In other words, where a+b=1 mol and ais less than 0.15 and b is more than 0.85, B₂O₃ that cannot formLn_(x)B_(y)O_(z) enters a liquid phase, thereby increasing the glassphase. Thus, the dielectric loss cannot be decreased. Where a+b=1 moland a is more than 0.55 and b is less than 0.45, the sinteringtemperature increases, and a ceramic composition composed of a densesinter cannot be obtained by the target low-temperature sintering.

Note that any of the rare earth elements represented by Ln can increasethe fQ value. Thus, in this invention, one or more rare earth elementscan be selected. In particular, when La and/or Nd is used as the rareearth element, an fQ value higher than that achieved by other rare earthelements can be obtained. However, the sintering temperature and thedielectric constant of the ceramic composition differ depending on thetype of rare earth element. Thus, these properties may be adequatelyadjusted by changing the type of the rare earth element or by changingthe content of the oxide RO of the alkaline earth metal element Rdescribed below.

The content of the each component described below is indicated in termsof a molar ratio with respect to one mole of the total of Ln₂O₃ andB₂O₃.

The content of the oxide RO of the alkaline earth metal element R is0.01 to 0.2 mol. At an RO content less than 0.01 mol, the sinteringtemperature cannot be decreased. At an RO content exceeding 0.2 mol, thetemperature characteristic τ_(f) of the resonant frequency becomes lowerthan −50 ppm/° C., i.e., excessively shifted toward the negative side,thereby increasing the temperature dependence.

At least one of MgO, CaO, SrO, and BaO may be used as the oxide RO ofthe alkaline earth metal R. In particular, the fQ value tends to belarger with CaO compared to that with oxides of other alkaline earthmetals.

Preferably, tungsten oxide WO₃ is contained in the ceramic compositionof the present invention. When WO₃ is contained, a dense sinter can beobtained by low-temperature sintering, which is the target of thepresent invention, while increasing the fQ value. In order to achievesuch an effect, WO₃ is preferably contained in an amount of 0.05 mol orless and more preferably in an amount of 0.005 to 0.05 mol. At a WO₃content exceeding 0.05 mol, the fQ value decreases, and the temperaturecharacteristic τ_(f) of the resonant frequency tends to significantlyshift toward the negative side. When the WO₃ content is less than 0.005mol, the above-described effect is not easily achieved. In the presentinvention, WO₃ is not an essential component.

The ceramic composition of the present invention preferably contains0.0005 to 0.002 mol of an oxide M₂O of an alkali metal element M. Inthis manner, the sintering temperature can be further decreased. Ingeneral, a glass composition containing alkali metal ions exhibits alarge dielectric loss and a small fQ value due to ionic induction. At anM₂O content of 0.002 mol or less, the fQ value is rarely affected. At anM₂O content of 0.0005 mol or more, the sintering temperature tends todecrease.

One or both of Al₂O₃ and TiO₂ in a total amount of 0.1 to 0.4 mol permole of the total of Ln₂O₃ and B₂O₃ are contained as the filler. At afiller content less than 0.1 mol, excessive deformation may occur duringsintering and the strength of the ceramic composition after thesintering may become insufficient. At a filler content exceeding 0.4mol, the sintering temperature is increased, and it may be difficult toconduct low-temperature sintering at 1,000° C. or less. In order toincrease the strength of the ceramic composition, Al₂O₃ may besingularly used or the content of Al₂O₃ may be increased. In order toincrease the dielectric constant of the ceramic composition, TiO₂ may besingularly used or the content of TiO₂ may be increased.

There are mainly two methods as the method for producing the ceramiccomposition of the present invention. According to a first method,powders of starting materials for ceramic composition are prepared, andthe powders are respectively weighed to yield a desired composition. Thepowders are wet-mixed in a ball mill, dried, and calcined at about 800°C. The resulting calcined material is pulverized to obtain a powder. Abinder is added to the powder, and the resulting mixture is kneaded andformed into a desired shape to obtain a compact. The compact is heatedto remove the binder and sintered to obtain the ceramic composition ofthe present invention.

According to a second method, powders of starting materials for theglass composition are prepared and respectively weighed to yield adesired composition. The powders are mixed with each other, and theresulting mixture is melted by heating at 1,000° C. or higher andrapidly cooled to produce a glass frit. The glass frit is pulverized.The filler was separately sintered and pulverized to prepare a powder.The glass frit, the filler, and the binder are mixed and kneaded, andformed into a compact. The binder is removed from the compact, and theresulting compact is sintered to prepare a ceramic composition of thepresent invention. In this second method, with respect to the glass fritcontaining Al₂O₃ and/or TiO₂ serving as the filler, it is possible tomix and knead the filler and the binder.

The above-described compact can be sintered at a temperature as low as800° C. to 1,000° C. At a sintering temperature less than 800° C., thesintering of the ceramic composition may not be insufficient, anddensity is not satisfactory. Thus, satisfactory strength may not beexhibited. When the ceramic composition of the present invention is usedas a material for a multilayer substrate and is sintered simultaneouslywith the material for metal wiring, the material for the metal wiringmay be heated to a temperature higher than the melting point and maystart to melt. However, at a temperature or 1,000° C. or less, thesintering can be performed without melting the material for the metalwiring, such as Cu or Ag. It should be noted that when Cu is used as thematerial for metal wiring, a reducing atmosphere is preferable to avoidpossible oxidation, and when Ag is used as the material for metalwiring, the sintering temperature is preferably up to 930° C.

The above-described materials for the ceramic composition are notnecessarily oxides as long as they are contained in the ceramiccomposition by forming oxides after the sintering. Thus, for example,carbonate salts, such as CaCO₃, and compounds, such as nitrides, e.g.,BN, other than oxides may be used as the starting materials. Althoughthese starting materials may contain impurities, they can be treated assingle compounds as long as the impurity content is 5 mass % or lesswith respect to the mass of the respective compound and the same effectscan be still be achieved.

In making a multilayer substrate having an integrated circuit by usingthe ceramic composition of the present invention, the material afterkneading is first formed into sheets to prepare green sheets, and aconductive paste containing the material for metal wiring is applied oneach green sheet by printing. A plurality of green sheets with theconductive paste applied thereon is stacked and sintered.

Here, a constraint sintering process in which the compact obtained bystacking a plurality of green sheets having the conductive paste appliedthereon by printing is sintered while applying pressure or constraint inthe vertical direction may be employed. According to this process, thecontraction due to sintering is limited in the vertical direction, i.e.,the Z direction, and no contraction occurs in the surface direction,i.e., the X-Y direction. A multilayer substrate having superior surfaceflatness can be accurately obtained as a result.

Preferably, green sheets composed of Al₂O₃ or the like that do notsinter at the sintering temperature of the ceramic composition areprovided on the upper and lower surfaces, respectively, of the compact,and the compact is preferably sintered while applying pressure orconstraint through these green sheets. Here, it is important that theAl₂O₃ green sheets on the upper and lower surfaces of the compact beeasily separable and that the metal wiring after the sinteringsufficiently adhere onto the ceramic composition so as to avoidconduction failure. Studies were conducted whether this process can beapplied to the ceramic composition. The results confirmed that thisprocess can be applied without any problem.

EXAMPLES

The starting material powders of the respective components wereadequately weighed to give ceramic compositions having compositionsshown in Tables 1 to 5. The starting material powders were all oxides.Deionized water was added to the starting material powders, and theresulting mixture was wet-mixed for 20 hours in a ball mill containingzirconia balls.

The resulting mixture was dried and calcined at 700° C. for 2 hours. Thecalcined mixture was pulverized to obtain a calcined powder. Thecalcined powder was combined with 10 mass % of a PVA aqueous solutionserving as a binder, and the resulting mixture was kneaded, granulated,and press-formed into a compact having a diameter of 15 mm and a heightof 7.5 mm. However, Samples 60, 61, and 62 shown in Table 3 wereprepared by melting the materials excluding the filler by heating to1,300° C., rapidly cooling the resulting materials to form a glass frit,adding a predetermined amount of the filler to the glass frit, adding 10mass % of a PVA aqueous solution serving as a binder to the resultingmixture, kneading and granulating the resulting mixture, andpress-forming the resulting mixture into a compact having a diameter of15 mm and a height of 7.5 mm.

These press-formed compacts were used as the samples. The temperature atwhich an experimental sintered compact prepared by sintering in thetemperature range of 800° C. to 1,250° C. is sufficiently dense isselected, and each sample was sintered at the corresponding selectedtemperature. Sintering of the sample was conducted after the sample washeated in air at 500° C. to 600° C. to remove the binder. The sinteringof the sample was conducted by heating the sample at the above-describedselected temperature for 2 hours.

The resulting cylindrical sinters were each polished to prepare a flatand smooth setter surface and then analyzed by a dielectric resonatormethod (short-circuited at both ends of a dielectric resonator) todetermine the relative dielectric constant εr and the Q value (Q=1/tanδ). Since the dielectric loss varies depending on the measurementresonant frequency fo, the dielectric loss was evaluated in terms of thefQ value, which is a product of fo and Q and is a constant valuedependent on the material of the sample but independent from thefrequency. The temperature characteristic τ_(f) of the resonancefrequency was determined from the rate of change in resonant frequencywith varying temperature with reference to the resonant frequency fo at25° C. The results of the measurement are shown in Tables 1 to 5.

TABLE 1 Composition of ceramic composition (molar ratio) Ln₂O₃ RO M₂OSample (Ln: Rare earth (R: Alkaline earth (M: Alkali metal Filler No.element) B₂O₃ metal element) WO₃ element) (Al₂O₃ or TiO₂)  1 La₂O₃:*0.1000 *0.9000  CaO: 0.0500 0.0100 0 Al₂O₃: 0.2000  2 La₂O₃: 0.15000.8500 CaO: 0.0500 0.0100 0 Al₂O₃: 0.2000  3 La₂O₃: 0.2500 0.7500 CaO:0.0500 0.0100 0 Al₂O₃: 0.2000  4 La₂O₃: 0.3333 0.6667 CaO: 0.0500 0.01000 Al₂O₃: 0.2000  5 La₂O₃: 0.4000 0.6000 CaO: 0.0500 0.0100 0 Al₂O₃:0.2000  6 La₂O₃: 0.5000 0.5000 CaO: 0.0500 0.0100 0 Al₂O₃: 0.2000  7La₂O₃: *0.6000 *0.4000  CaO: 0.0500 0.0100 0 Al₂O₃: 0.2000  8 La₂O₃:*0.6667 *0.3333  CaO: 0.0500 0.0100 0 Al₂O₃: 0.2000  9 La₂O₃: 0.25000.7500 *0 0.0100 0 Al₂O₃: 0.2000 10 La₂O₃: 0.2500 0.7500 CaO: 0.01000.0100 0 Al₂O₃: 0.2000 11 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0100 0Al₂O₃: 0.2000 12 La₂O₃: 0.2500 0.7500 CaO: 0.2000 0.0100 0 Al₂O₃: 0.200013 La₂O₃: 0.2500 0.7500 CaO: *0.2500 0.0100 0 Al₂O₃: 0.2000 14 La₂O₃:0.2500 0.7500 CaO: 0.1000 0.0100 0 Al₂O₃: 0.2000 15 La₂O₃: 0.2500 0.7500CaO: 0.1000 0.0100 0 Al₂O₃: 0.2000 16 La₂O₃: 0.2500 0.7500 CaO: 0.10000.0300 0 Al₂O₃: 0.2000 17 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0500 0Al₂O₃: 0.2000 18 La₂O₃: 0.2500 0.7500 CaO: 0.1000 *0.0700  0 Al₂O₃:0.2000 19 La₂O₃: 0.2500 0.7500 CaO: 0.1000 *0.1000  0 Al₂O₃: 0.2000 20La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0100 0 Al₂O₃: 0.1000 21 La₂O₃: 0.25000.7500 CaO: 0.1000 0.0100 0 Al₂O₃: 0.3000 22 La₂O₃: 0.2500 0.7500 CaO:0.1000 0.0100 0 Al₂O₃: 0.4000 23 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.01000 Al₂O₃: 0.5500 24 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0100 0 Al₂O₃:0.6000 25 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0100 0 Al₂O₃: 0.1000Characteristics of ceramic composition Relative Temperature Sinteringdielectric characteristic Resonant Sample temperature constant fQ τ_(f)frequency No. (° C.) ε_(r) (GHz) (ppm/° C.) f₀ (GHz) Remarks  1 800 9.17500 −41 13.5 Comparative Example  2 825 9.5 16500 −36 13.2 InventionExample  3 850 10.1 15600 −35 13.0 Invention Example  4 850 10.0 16000−20 12.0 Invention Example  5 900 11.0 17500 −15 12.9 Invention Example 6 950 11.5 21000 −17 12.7 Invention Example  7 1200  11.8 10200 −2512.4 Comparative Example  8 1250  10.3 15000 −20 13.5 ComparativeExample  9 1150  11.8 17000 −25 12.0 Comparative Example 10 1000  11.517500 −30 11.7 Invention Example 11 950 11.7 17200 −37 11.2 InventionExample 12 900 11.4 16800 −42 11.4 Invention Example 13 950 10.2 15800−73 13.1 Comparative Example 14 900 11.8 16800 −31 11.4 InventionExample 15 900 10.0 17200 −31 12.7 Invention Example 16 850 10.2 18500−35 12.4 Invention Example 17 850 10.1 17500 −39 12.8 Invention Example18 850 9.8 7200 −59 13.1 Comparative Example 19 850 9.8 4300 −70 13.1Comparative Example 20 850 9.2 17400 −32 12.2 Invention Example 21 9009.1 18000 −37 13.0 Invention Example 22 950 8.5 18100 −38 13.9 InventionExample 23 1100  7.8 12000 −29 14.0 Comparative Example 24 1150  7.19500 −13 14.1 Comparative Example 25 910 10.0 16500 −31 12.1 InventionExample Asterisks indicate that the marked features are outside thescope of the present invention.

TABLE 2 Composition of ceramic composition (molar ratio) Ln₂O₃ RO M₂OSample (Ln: Rare earth (R: Alkaline earth (M: Alkali metal Filler No.element) B₂O₃ metal element) WO₃ element) (Al₂O₃ or TiO₂) 26 La₂O₃:0.2500 0.7500 CaO: 0.1000 0.0100 0 TiO₂: 0.3000 27 La₂O₃: 0.2500 0.7500CaO: 0.1000 0.0100 0 TiO₂: 0.4000 28 La₂O₃: 0.2500 0.7500 CaO: 0.10000.0100 0 TiO₂: *0.5000 29 Nd₂O₃: *0.1000 *0.9000 CaO: 0.1000 0 0 Al₂O₃:0.1500 30 Nd₂O₃: 0.1500 0.8500 CaO: 0.1000 0 0 Al₂O₃: 0.1500 31 Nd₂O₃:0.2500 0.7500 CaO: 0.1000 0 0 Al₂O₃: 0.1500 32 Nd₂O₃: 0.3300 0.6700 CaO:0.1000 0 0 Al₂O₃: 0.1500 33 Nd₂O₃: 0.4000 0.6000 CaO: 0.1000 0 0 Al₂O₃:0.1500 34 Nd₂O₃: 0.5000 0.5000 CaO: 0.1000 0 0 Al₂O₃: 0.1500 35 Nd₂O₃:0.5500 0.4500 CaO: 0.1000 0 0 Al₂O₃: 0.1500 36 Nd₂O₃: *0.6000 *0.4000CaO: 0.1000 0 0 Al₂O₃: 0.1500 37 La₂O₃: 0.1000 0.8000 CaO: 0.1000 0 0Al₂O₃: 0.1500 Nd₂O₃: 0.1000 38 La₂O₃: 0.2000 0.6000 CaO: 0.1000 0 0Al₂O₃: 0.1500 Nd₂O₃: 0.2000 39 La₂O₃: 0.3000 0.5000 CaO: 0.1000 0 0Al₂O₃: 0.1500 Nd₂O₃: 0.2000 40 La₂O₃: 0.3000 0.5000 CaO: 0.1000 0 0Al₂O₃: 0.1500 Nd₂O₃: 0.2000 41 La₂O₃: *0.3000 *0.4000 CaO: 0.1000 0 0Al₂O₃: 0.1500 Nd₂O₃: *0.3000 42 La₂O₃: 0.3333 0.6667 BaO: 0.1000 0 0Al₂O₃: 0.1500 43 La₂O₃: 0.3333 0.6667 BaO: 0.1000 0 0 Al₂O₃: 0.1500 44La₂O₃: 0.3333 0.6667 BaO: *0.2500 0 0 Al₂O₃: 0.1500 45 La₂O₃: 0.33330.6667 SrO: 0.0100 0 0 Al₂O₃: 0.1500 Characteristics of ceramiccomposition Relative Temperature Sintering dielectric characteristicResonant Sample temperature constant fQ τ_(f) frequency No. (° C.) ε_(r)(GHz) (ppm/° C.) f₀ (GHz) Remarks 26 915 12.1 17200 −25 12.4 InventionExample 27 950 14.1 15000 −20 11.8 Invention Example 28 1125 14.3 9300−25 11.1 Comparative Example 29 850 9.3 7200 −36 13.8 ComparativeExample 30 900 10.2 16800 −39 12.4 Invention Example 31 925 10.8 17500−30 12.1 Invention Example 32 925 11.0 16000 −25 11.0 Invention Example33 950 12.0 18000 −20 11.2 Invention Example 34 950 11.8 17500 −15 11.5Invention Example 35 950 11.5 15200 −14 11.7 Invention Example 36 105010.1 11300 −21 10.9 Comparative Example 37 900 10.5 17500 −30 12.2Invention Example 38 950 11.8 18000 −18 11.9 Invention Example 39 90011.7 17000 −14 11.6 Invention Example 40 900 11.8 18000 −13 11.5Invention Example 41 1025 9.8 6300 −21 14.3 Comparative Example 42 95010.6 15600 −35 10.1 Invention Example 43 1000 11.0 15000 −45 11.0Invention Example 44 950 11.5 16200 −71 11.1 Comparative Example 45 10009.9 15000 −38 10.2 Invention Example Asterisks indicate that the markedfeatures are outside the scope of the present invention.

TABLE 3 Composition of ceramic composition (molar ratio) Ln₂O₃ RO M₂OSample (Ln: Rare earth (R: Alkaline earth (M: Alkali metal Filler No.element) B₂O₃ metal element) WO₃ element) (Al₂O₃ or TiO₂) 46 La₂O₃:0.3333 0.6667 SrO: 0.1000 0 0 Al₂O₃: 0.1500 47 La₂O₃: 0.3333 0.6667 SrO:*0.2500 0 0 Al₂O₃: 0.1500 48 La₂O₃: 0.3333 0.6667 CaO: 0.0500 0 0 Al₂O₃:0.1500 BaO: 0.0100 49 La₂O₃: 0.3333 0.6667 CaO: 0.1000 0 0 Al₂O₃: 0.1500BaO: 0.0500 50 La₂O₃: 0.3333 0.6667 CaO: 0.1000 0 0 Al₂O₃: 0.1500 SrO:0.0500 51 La₂O₃: 0.3333 0.6667 BaO: 0.0100 0 0 Al₂O₃: 0.1500 SrO: 0.050052 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0 Li₂O: 0.0010 Al₂O₃: 0.1500 53La₂O₃: 0.2500 0.7500 CaO: 0.1000 0 Li₂O: 0.0020 Al₂O₃: 0.1500 54 La₂O₃:0.2500 0.7500 CaO: 0.1000 0 Li₂O: *0.0025 Al₂O₃: 0.1500 55 La₂O₃: 0.25000.7500 BaO: 0.0100 0 Li₂O: 0.0010 Al₂O₃: 0.1500 56 La₂O₃: 0.3333 0.6667SrO: 0.1000 0 Li₂O: 0.0010 Al₂O₃: 0.1500 57 La₂O₃: 0.3333 0.6667 CaO:0.1000 0 Na₂O: 0.0010 Al₂O₃: 0.1500 58 La₂O₃: 0.3333 0.6667 CaO: 0.10000 Na₂O: 0.0020 Al₂O₃: 0.1500 59 La₂O₃: 0.3333 0.6667 CaO: 0.1000 0 Na₂O:*0.0025 Al₂O₃: 0.1500 60 La₂O₃: 0.3333 0.6667 CaO: 0.1000 0 Li₂O: 0.0010Al₂O₃: 0.1500 Na₂O: 0.0010 61 La₂O₃: 0.3333 0.6667 CaO: 0.1000 0 Li₂O:0.0010 Al₂O₃: 0.1500 K₂O: 0.0010 62 La₂O₃: 0.3333 0.6667 CaO: 0.1000 0K₂O: 0.0010 Al₂O₃: 0.1500 Na₂O: 0.0010 Characteristics of ceramiccomposition Relative Temperature Sintering dielectric characteristicResonant Sample temperature constant fQ τ_(f) frequency No. (° C.) ε_(r)(GHz) (ppm/° C.) f₀ (GHz) Remarks 46 1000  10.2 15000 −35 10.2 InventionExample 47 950 10.8 12500 −70 10.2 Comparative Example 48 980 11.0 15200−45 10.2 Invention Example 49 980 11.5 15000 −38 9.8 Invention Example50 950 10.2 15000 −35 10.0 Invention Example 51 980 11.5 15000 −40 10.1Invention Example 52 900 11.7 14500 −38 9.8 Invention Example 53 850 9.815500 −40 8.0 Invention Example 54 800 6.8 <2000 Immeasurable 7.8Comparative Example 55 900 12.0 15100 −35 10.1 Invention Example 56 85011.0 15300 −39 10.5 Invention Example 57 850 10.2 15000 −35 11.3Invention Example 58 800 8.0 15100 −36 12.1 Invention Example 59 800 5.0<2000 Immeasurable 15.8 Comparative Example 60 **800  8.5 16100 −38 11.8Invention Example 61 **825  8.8 15000 −40 11.6 Invention Example 62**825  9.0 15500 −38 11.3 Invention Example Asterisks indicate that themarked features are outside the scope of the present invention. Doubleasterisks indicate that the filler was mixed after preparation of theglass frit, and the resulting mixture was then sintered.

TABLE 4 Composition of ceramic composition (molar ratio) Ln₂O₃ RO M₂OSample (Ln: Rare earth (R: Alkaline earth (M: Alkali metal Filler No.element) B₂O₃ metal element) WO₃ element) (Al₂O₃ or TiO₂) 63 La₂O₃:0.3333 0.6667 CaO: 0.1000 0 Rb₂O: 0.0010 Al₂O₃: 0.1500 64 La₂O₃: 0.33330.6667 CaO: 0.1000 0 Cs₂O: 0.0010 Al₂O₃: 0.1500 65 La₂O₃: 0.3333 0.6667CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.1500 66 La₂O₃: 0.3333 0.6667CaO: 0.1000 0.0300 Li₂O: 0.0010 Al₂O₃: 0.1500 67 La₂O₃: 0.3333 0.6667CaO: 0.1000 0.0500 Li₂O: 0.0010 Al₂O₃: 0.1500 68 La₂O₃: 0.3333 0.6667CaO: 0.1000 *0.0600 Li₂O: 0.0010 Al₂O₃: 0.1500 69 Nd₂O₃: 0.3333 0.6667CaO: 0.1000 0.0300 Li₂O: 0.0010 Al₂O₃: 0.1500 70 Nd₂O₃: 0.3333 0.6667CaO: 0.1000 0.0500 Li₂O: 0.0010 Al₂O₃: 0.1500 71 Nd₂O₃: 0.3333 0.6667CaO: 0.1000 *0.0600 Li₂O: 0.0010 Al₂O₃: 0.2000 72 La₂O₃: 0.2500 0.7500CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.1000 TiO₂: 0.1000 73 La₂O₃:0.2500 0.7500 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.2000 TiO₂: 0.100074 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.2500TiO₂: 0.2500 75 Nd₂O₃: 0.2500 0.7500 CaO: 0.0500 0.0100 Li₂O: 0.0010Al₂O₃: 0.2000 BaO: 0.0500 76 La₂O₃: 0.2000 0.6000 CaO: 0.1000 0.0100Li₂O: 0.0010 Al₂O₃: 0.1000 Nd₂O₃: 0.2000 BaO: 0.0500 Na₂O: 0.0010 TiO₂:0.1000 77 La₂O₃: 0.1500 0.7000 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃:0.3000 Nd₂O₃: 0.1500 BaO: 0.0500 78 La₂O₃: 0.2000 0.6667 CaO: 0.10000.0100 Li₂O: 0.0010 Al₂O₃: 0.1000 Nd₂O₃: 0.1333 79 La₂O₃: 0.2333 0.6667CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.1000 Nd₂O₃: 0.1000Characteristics of ceramic composition Relative Temperature Sinteringdielectric characteristic Resonant Sample temperature constant fQ τ_(f)frequency No. (° C.) ε_(r) (GHz) (ppm/° C.) f₀ (GHz) Remarks 63 850 8.715000 −35 12.1 Invention Example 64 850 8.5 15000 −33 13.0 InventionExample 65 850 10.2 16000 −40 12.0 Invention Example 66 850 7.8 15500−45 13.8 Invention Example 67 850 7.0 15000 −49 13.5 Invention Example68 800 6.8 9500 −65 14.0 Comparative Example 69 850 7.5 16000 −41 13.8Invention Example 70 800 6.8 15000 −48 13.3 Invention Example 71 800 6.36300 −68 14.3 Comparative Example 72 950 11.3 16800 −33 10.8 InventionExample 73 1000 13.1 17200 −35 10.2 Invention Example 74 1150 13.8 16000−38 10.0 Comparative Example 75 1000 12.1 16000 −30 10.5 InventionExample 76 900 11.8 15800 −25 11.0 Invention Example 77 950 9.5 15000−30 12.1 Invention Example 78 900 10.0 15500 −35 10.8 Invention Example79 900 10.5 15000 −40 11.5 Invention Example Asterisks indicate that themarked features are outside the scope of the present invention.

TABLE 5 Composition of ceramic composition (molar ratio) Ln₂O₃ RO M₂OSample (Ln: Rare earth (R: Alkaline earth (M: Alkali metal Filler No.element) B₂O₃ metal element) WO₃ element) (Al₂O₃ or TiO₂) 80 La₂O₃:0.3333 0.6667 CaO: 0.0500 0.0100 Li₂O: 0.0010 Al₂O₃: 0.1000 BaO: 0.0500Na₂O: 0.0010 81 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0100 Li₂O: 0.0010Al₂O₃: 0.1000 SrO: 0.1000 82 La₂O₃: 0.2500 0.7500 CaO: 0.1000 0.0100Li₂O: 0.0020 Al₂O₃: 0.1000 83 La₂O₃: 0.3333 0.6667 CaO: 0.1000 0.0100Li₂O: 0.0010 Al₂O₃: 0.2000 TiO₂: 0.2000 84 La₂O₃: 0.3333 0.6667 CaO:0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: *0.3000 TiO₂: *0.3000 85 Nd₂O₃: 0.25000.7500 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.3000 86 Nd₂O₃: 0.33330.6667 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.4000 87 Nd₂O₃: 0.50000.5000 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.3000 88 Nd₂O₃: 0.50000.5000 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.3000 K₂O: 0.0010 89Nd₂O₃: 0.5000 0.5000 CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.3000 BaO:0.1000 90 Nd₂O₃: 0.5000 0.5000 CaO: 0.1000 0.0200 Li₂O: 0.0010 Al₂O₃:0.3000 BaO: 0.1000 91 La₂O₃: 0.2500 0.5000 CaO: 0.1000 0.0500 Li₂O:0.0010 Al₂O₃: 0.3000 Nd₂O₃: 0.2500 BaO: 0.1000 92 La₂O₃: 0.3000 0.4500CaO: 0.1000 0.0100 Li₂O: 0.0010 Al₂O₃: 0.3000 Nd₂O₃: 0.2500 BaO: 0.1000Characteristics of ceramic composition Relative Temperature Sinteringdielectric characteristic Resonant Sample temperature constant fQ τ_(f)frequency No. (° C.) ε_(r) (GHz) (ppm/° C.) f₀ (GHz) Remarks 80 850 8.517500 −38 14.0 Invention Example 81 850 10.3 16500 −35 12.5 InventionExample 82 850 10.2 16500 −36 12.5 Invention Example 83 1000 11.5 17000−30 10.5 Invention Example 84 1150 10.8 7400 −35 12.2 ComparativeExample 85 1000 11.0 15000 −33 11.8 Invention Example 86 1000 11.2 16000−38 11.2 Invention Example 87 1000 11.1 15800 −35 11.8 Invention Example88 980 12.1 15000 −30 9.7 Invention Example 89 950 11.8 16500 −40 11.5Invention Example 90 950 10.5 15500 −41 12.0 Invention Example 91 90010.3 15000 −38 11.5 Invention Example 92 1000 10.4 15500 −40 10.3Invention Example Asterisks indicate that the marked features areoutside the scope of the present invention.

The results shown in Table 1 to 5 show that nearly all of the inventionexamples exhibited an fQ value of 15,000 GHz or more, a low dielectricloss in the high-frequency band, and a resonant frequency temperaturecoefficient τ_(f) of within ±50° C./ppm. This is presumably due to theeffect of incorporating Ln₂O₃ into the glass composition together withthe filler. At a small Ln₂O₃ content, the fQ value is low, as shown bySamples 1 in Table 1 and Sample 29 in Table 2.

The invention examples produced sufficiently dense sinters having highfQ values even at a sintering temperature of 1,000° C. or less. This isbecause the contents of the Ln₂O₃, RO, Al₂O₃, and TiO₂ are limitedwithin particular ranges. This fact is clearly supported by the resultsof Samples 7, 8, 9, 23, 24, 28, 36, 41, 47, 74, and 84 compositionswhich were outside the ranges of the invention, since they did notachieve the target fQ value or they required high sinteringtemperatures.

RO has an effect of decreasing the sintering temperature. However, at anexcessively large RO content, the temperature coefficient τ_(f) of theresonant frequency tends to be excessively shifted toward the negativeside, as shown by Samples 13, 44, and 47.

Incorporation of WO₃ or M₂O decreases the sintering temperature, and WO₃or M₂O can be effectively used by controlling its content. At anexcessively large content, however, a significant decrease in fQ valueor degradation of temperature coefficient τ_(f) may result, as shown bySamples 18, 19, 54, 59, 68, and 71.

INDUSTRIAL APPLICABILITY

A ceramic composition of the present invention has a low dielectric lossin the high-frequency band and low temperature dependence of theresonant frequency. Moreover, since its characteristics can be exhibitedat a low sintering temperature, a metal, such as Ag or Cu, having a lowspecific resistance can be used as the material for the metal wiring orelectrode, and the conductor loss can thus be decreased. The ceramiccomposition of the present invention is thus suitable for the substratematerials for high-frequency band multilayer substrates and thematerials for electronic components.

1. A ceramic composition comprising a glass composition and 0.1 to 0.4mol of a filler which is at least one of Al₂O₃ and TiO₂, wherein thecomposition of the glass composition comprises 0.15 to 0.55 mol of awhich is an oxide or oxide precursor of a rare earth element or mixturesthereof, 0.45 to 0.85 mol of b which is boron oxide B₂O₃ or an oxideprecursor thereof, wherein a+b=1 mol, and 0.01 to 0.2 mol of an oxide oroxide precursor of an alkaline earth metal element.
 2. The ceramiccomposition according to claim 1, comprising a positive amount of up to0.05 mol of tungsten oxide or an oxide precursor thereof.
 3. The ceramiccomposition according to claim 2 in which the amount of tungsten oxideor precursor is at least 0.005 mol.
 4. The ceramic composition accordingto claim 3, comprising 0.0005 to 0.002 mol of an oxide or oxideprecursor of an alkali metal element M.
 5. The ceramic compositionaccording to claim 2, comprising 0.0005 to 0.002 mol of an oxide oroxide precursor of an alkali metal element M.
 6. The ceramic compositionaccording to claim 1 which contains 0.0005 to 0.002 mol of an oxide oroxide precursor of an alkali metal.
 7. The ceramic composition accordingto claim 1 in which the rare earth element is at least one of La and Nd.8. The ceramic composition according to claim 1 in which the alkalineearth metal comprises Ca.
 9. The ceramic composition according to claim1 in which the filler comprises Al₂O₃.
 10. The ceramic compositionaccording to claim 1 in which the filler comprises TiO₂.
 11. The ceramiccomposition according to claim 1 in which each of the oxides orprecursors is the oxide.
 12. The ceramic composition according to claim11, comprising a positive amount of up to 0.05 mol of tungsten oxide.13. The ceramic composition according to claim 12, comprising 0.0005 to0.002 mol of an oxide of an alkali metal element, and in which the rareearth element is at least one of La and Nd, and the alkaline earth metalcomprises Ca.
 14. The ceramic composition according to claim 13 in whichthe filler comprises Al₂O₃.
 15. The ceramic composition according toclaim 14, in which the tungsten oxide amount is 0.005 to 0.05 mol. 16.The ceramic composition according to claim 13 in which the fillercomprises TiO₂.
 17. A compact comprising a sintered composition of claim16.
 18. A compact comprising a sintered composition of claim
 14. 19. Acompact comprising a sintered composition of claim
 10. 20. A compactcomprising a sintered composition of claim
 9. 21. A compact comprising asintered composition of claim 1.